Fracture Characteristics and Their Influence on Gas Seepage in Tight Gas Reservoirs in the Kelasu Thrust Belt (Kuqa Depression, NW China)

Yue Dong, Xuesong Lu, Junjia Fan and Qingong Zhuo
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Yue Dong: School of Energy Resources, China University of Geosciences, Beijing 100083, China
Xuesong Lu: Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
Junjia Fan: Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China
Qingong Zhuo: Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China

Energies, 2018, vol. 11, issue 10, 1-22

Abstract: Natural fractures were generally accepted as a key factor influencing the gas seepage performance in tight gas reservoirs in Kelasu Thrust Belt (KTB). However, the mechanism was not fully clarified, especially from a microscopic perspective. Based on observation of core samples and cast thin sections and gas charging experiment on core plugs, the parameters of fractures and seepage performance in fractured tight reservoirs are studied; further, the controlling effect of fractures on gas seepage was discussed. The results show that in KTB fractures could be categorized by the size of their apertures as macro-fractures (aperture width ranges from 0.1 to 2 mm) and micro-fractures (aperture width ranges from 5 to 100 μm), which appear in the form of fractures networks. Tectonic deformations and abnormal high fluid pressure control the fracture density: near faults or anticlines (folds), fracture density increases, and fluid pressure of 15 MPa increases the aperture by 50%, and induces new fractures. The fracture networks with high linear density significantly improves tight reservoir quality and seepage performance: it enhances the reservoir permeability by 1–4 orders of magnitude, and the relative gas permeability by 2–10 magnitude; by enhancing permeability, the fracture networks reduce the initial flowing gradient from as high as 0.41 MPa/cm to 0 Mpa/cm, and make the gas flowing possible.

Keywords: tight sandstone reservoirs; gas seepage; initial flowing pressure gradient; Kelasu Thrust Belt; Kuqa Depression (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
References: View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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